Oil Comparison for Weighing Precipitation Gauges as used in Environment Canada TECO-2014 St. Petersburg, Russian Federation July 9, 2014 Jeffery Hoover, Hagop Mouradian, Mike Earle, Kai Wong, Sorin Pinzariu, Rodica Nitu Meteorological Service of Canada- Environment Canada Toronto, Ontario, Canada
Outline 1. Objective and background 2. Important factors 3. Evaluation criteria 4. Density 5. Kinematic viscosity 6. Evaporation comparison 7. Conclusions Page 2
Objective Objective: Establish principles and recommendations for the selection of oil in precipitation weighing gauges. Current Meteorological Service of Canada usage, by Regions: Region Pacific and Yukon Prairie and Northern Ontario Quebec Atlantic Precipitation Gauge Oil Mineral Oil, Baby Oil VoltEsso 35, Shell Diala Oil AX Bayol 35 (discontinued) Bayol 35 (discontinued), Isopar M Bayol 35 (discontinued) Antifreeze used: 60% Methanol & 40% Propylene Glycol Desired outcome: identify oils that could be used operationally in the networks operated by the Meteorological Service of Canada Page 3
Important Factors Precipitation (rain, snow, mixed) oil Operational Temp: -40 C to 60 C bucket anti-freeze solution Oil Benefits: Limit evaporation of precip & anti-freeze Reduce splashing Oil Requirements: Floats on precipitation & anti-freeze solution Enables light snow and rain penetration Does not evaporate and limits evaporation within bucket Does not mix with water Does not react with bucket or liquid mixture Is not harmful to human exposure Presence & condition is clearly visible Does not attract animals & insects Page 4
Evaluation Criteria Oil floats on liquid Purpose Parameter Evaluation Criteria Oil enables light snow and water penetration Density Viscosity & Surface Tension ρ < Anti-freeze & precipitation mixture Low density is best Low viscosity is best Low surface tension is best Oil does not evaporate Evaporation rate Low evaporation is best Oil does not mix with water Water solubility Immiscible in water Oil does not react with bucket or liquid mixture Oil is not harmful to human exposure Oil presence and condition is clearly visible Oil does not attract animals & insects Non-reactive Toxicity Colour Odor Must not react with plastic bucket & anti-freeze solution Low toxicity for reduced health risks Visible to show oil presence, coverage and elevation within bucket Limited odor to not attract animals Page 5
Precipitation Gauge Oil Comparison Test Samples Oil Samples 1 Clearco silicone oil, 2 mm 2 /s 2 Clearco silicone oil, 5 mm 2 /s 3 Clearco silicone oil, 10 mm 2 /s 4 Bayol 35 (isoparaffinic hydrocarbon) 5 Isopar M (isoparaffinic hydrocarbon) 6 Mobil Aero HFA (hydraulic oil) 7 Univis HVI 13 (hydraulic oil) 8 Voltesso 35 (electrical insulating oil) 9 Baby oil (mineral oil base) 10 Raw linseed oil 1 2 3 4 5 Anti-Freeze Samples Empty bucket [40% PG / 60% M] Full bucket -20 C mixture [16% PG / 24% M / 60% DW] Full bucket -40 C mixture [22% PG / 33% M / 45% DW] Empty bucket alternative [75% PG / 25% DW] Full bucket alternative [25% PG / 75% DW] PG Propylene Glycol M Methanol DW Distilled Water Page 6
Viscosity µ (ASTM D 7042) ASTM D 7042 - Standard Test Method for Dynamic Viscosity and Density of Liquids by Stabinger Viscometer Test method for Newtonian fluids such as petroleum products and crude oils. Drying agent 1 Test sample Anton Paar SVM3000 Cooling bath 1 Newtonian fluid: Shear stress τ µ Slope = viscosity u τ = µ y 1. http://www.anton-paar.com/ca-en/products/group/viscometer/ Velocity gradient u y Page 7
Surface Tension γ Will solid precipitation (dendrites, plates, needles...) pass through the oil surface at cold temperatures? air snowflake oil 4 4 Liquid Surface Tension (mn/m) Water 0 C, 100 kpa 75.64 [1] Silicone oil 2 cst 18.7 [2] 5 5 Light object supported on surface by hydrostatic pressure and surface tension [3] Lower surface tension will have less ability to hold an object at its surface Degree of wetting of snow at snow-oil interface at cold temps? 1. CRC Handbook of Chemistry and Physics, 2004. 2. Clearco properties of polydimethylsiloxane fluids 3. Mansfield, E. H. Et al. Equilibrium and mutual attraction or repulsion of objects supported by surface tension, Phil Trans R Soc, May 1997. 4. http://en.wikipedia.org/wiki/surface_tension 5. http://www.dpchallenge.com Page 8
Viscosity µ (ASTM D 7042) Based on results from tests conducted by the Meteorological Service of Canada Dynamic Viscosity (mpa-s) 10 4 Dynamic Viscosity ASTM D 7042 10 3 10 2 10 1 10 0 Silicone 2 cst -40 C -20 C 0 C high viscosity Silicone 5 cst Silicone 10 cst Bayol 35 Isopar M Mobil Aero HFA Univis HVI 13 Voltesso 35 * Baby Oil Raw Linseed Oil 850x µ water µ honey = ~2000+ mpa s [1] * 40%PG/60%M * 22%PG/33%M/45%DW 16%PG/24%M/60%DW 75%PG/25%DW * 25%PG/75%DW µ water 0 C 100 kpa = 1.793 mpa s [2] * Product too viscous or solid to get a result Oil Samples Anti-Freeze Samples Page 9 1. http://en.wikipedia.org/wiki/viscosity, April 2, 2014 2. CRC Handbook of Chemistry and Physics, 2004
Density (ASTM D 7042) Based on results from tests conducted by the Meteorological Service of Canada Density (g/cm 3 ) 1.1 1.05 1 0.95 0.9 0.85-40 C -20 C 0 C Density ASTM D 7042 high density low density * * * * Propylene glycol mix is denser than water ρ water 0 C 100 kpa = 0.99984 g/cm 3 [1] ρ ice 0 C = 0.9167 g/cm 3 [1] 0.8 0.75 0.7 Silicone 2 cst Silicone 5 cst Silicone 10 cst Bayol 35 Isopar M Mobil Aero HFA Univis HVI 13 Voltesso 35 Baby Oil Raw Linseed Oil 40%PG/60%M 16%PG/24%M/60%DW 22%PG/33%M/45%DW 75%PG/25%DW 25%PG/75%DW * Product too viscous or solid to get a result Oil Samples Anti-Freeze Samples Page 10 1. CRC Handbook of Chemistry and Physics, 2004
Evaporation (Lab Experiment) Gill MetPak Samples - Samples added to petri dish up to fill line Vaisala PTB220 Ohaus Explorer EX10202 Precision scale - Petri dish area estimated from x, y measurements - Measurements of sample mass over 1 week period - Testing performed indoors - Lights were on during business hours Page 11 Samples 1 Clearco silicone oil, 2 cst 2 Clearco silicone oil, 5 cst 3 Clearco silicone oil, 10 cst 4 Bayol 35 (isoparaffinic hydrocarbon) 5 Isopar M (isoparaffinic hydrocarbon) 6 Mobil Aero HFA (hydraulic oil) 7 Univis HVI 13 (hydraulic oil) 8 Voltesso 35 (electrical insulating oil) 9 Baby oil (mineral oil base) 10 Raw linseed oil 11 Anti-freeze [40% PG / 60% M] 12 Propylene Glycol USP FCC 13 Methanol ACS 14 Distilled Water ACS 15 Tap Water PG Propylene Glycol USP FCC M Methanol ACS
Evaporation (Lab Experiment) Evaporation Rate Relative to Distilled Water (g/cm 2 /hr / g/cm 2 /hr) 5 4 3 2 1 0 Low evaporation rate for all oil samples tested Anti-freeze mixture evaporates ~2.5x faster than water Methanol evaporates ~5x faster than water Silicone 2 cst Silicone 5 cst Silicone 10 cst Bayol 35 Isopar M Mobil Aero HFA Univis HVI 13 Voltesso 35 Baby Oil Raw Linseed Oil 40%P.G./60%M. Propylene Glycol Methanol Distilled Water Tap Water Box plot: Red line: Median Box: 25 % & 75 % Whiskers: Min & Max Page 12
Evaporation (Lab Experiment) Evaporation Rate Relative to Distilled Water (g/cm 2 /hr / g/cm 2 /hr) 0.03 0.025 0.02 0.015 0.01 0.005 0-0.005 ~40x slower than water ~50x slower than water Silicone 2 cst Silicone 5 cst Silicone 10 cst Bayol 35 Isopar M Mobil Aero HFA Univis HVI 13 Voltesso 35 Baby Oil Raw Linseed Oil Box plot: Red line: Median Box: 25 % & 75 % Whiskers: Min & Max Page 13
Isopar M Oil Performance Summary Purpose Parameter Evaluation Criteria Performance Oil floats on liquid Oil enables light snow and water penetration Oil does not evaporate Oil does not mix with water Oil does not react with bucket or liquid mixture Oil is not harmful to human exposure Oil presence and condition is clearly visible Oil does not attract animals & insects Density Viscosity & Surface Tension Evaporation rate ρ < Anti-freeze & precip mix Low density is best Low viscosity is best Low surface tension is best Low evaporation is best ρ= 0.82 g/cm 3 @ -40 C (ASTM D 7042) Lower than other oil types tested µ = 100.9 MPa s @ -40 C (ASTM D 7042) Lower viscosity than other oil types tested ~ 50x slower evaporation than water Water solubility Immiscible in water Immiscible in water Non-reactive Toxicity Colour Odor Must not react with plastic bucket & anti-freeze solution Low toxicity for reduced health risks Visible to show oil presence, coverage and elevation within bucket Limited odor to not attract animals Non-reactive with plastic, methanol, & propylene glycol HMIS Hazard ID: Health 1, Flammability 1, Reactivity 1 Colourless. Dye can be added to achieve desired color. Odorless Page 14
Conclusions Bayol 35 & Isopar M oil provide the best combination of low density and low viscosity for use in operations (compared with the other oils tested) The addition of oil for all gauges using volatile anti-freeze solutions such as 40 % Propylene Glycol / 60 % Methanol, would ensure the performance of the anti-freeze solution. The hygroscopic propylene glycol and water antifreeze solution exhibits high viscosity and density at low temperatures, which may lead to stratification and slush and ice accumulation at the surface. Page 15
Precipitation Gauge Oil Comparison Thank-you Corresponding author: jeffery.hoover@ec.gc.ca Page 16